1. Field of the Invention.
This invention relates to a portable tree step which can be rapidly fastened into a tree, just as rapidly removed and which can be folded to be easily stored and carried by an outdoorsman.
2. Description of the Prior Art.
I developed the first known portable tree step in the early 1960's, and obtained on it U.S. Pat. No. 3,298,459 granted to Bergsten in June of 1967. It was a rigid metallic crank-like structure including a large wood screw integral with and extending outwardly from the upper end of an elongated support leg, and an elongated step portion integral with and extending outwardly in an opposite direction from the lower end of the support leg. Portable steps made according to my invention were effective and were widely used, but they were found to be somewhat difficult to get started into the tree when the user was standing part way up the tree and did not have free use of both of his hands and arms for installing the step.
Others attempted to improve on my invention, and the following patents were issued:
______________________________________ U.S. Pat. No. Patentee Granted ______________________________________ 3,380,697 Melcher April 1968 3,498,409 Meyer March 1970 4,413,706 Michael November 1983 ______________________________________
The patent to Michael discloses a tree step having a partly channel-shape central leg 15, with the channel legs of the central leg extending out beyond the channel portion and with a straight pivot pin receiving slot being provided in each of those channel legs. A step 14 is connected to a lower end portion of the central leg by a pivot pin in such a manner that the step can be moved from a working position at 90.degree. to the central leg to a storage position in nesting relationship to the central leg. When nested together, the open side of the step and central leg channels face in opposite directions. A tapered wood screw 16 is mounted on a screw pivot pin which slides in the pivot pin receiving slots of the central leg, and the screw can move from encompassed relation between the nested central leg and foot, to an extended position 180.degree. from its nested position, and to a working position 270.degree. from its original nesting position. By positioning the screw in its extended position and sliding it back so that the screw pivot pin is in the "lower end" end of the pin receiving slots, the first few threads of the screw can be driven into a tree, and the nested foot and central leg can be rotated to start the screw into holding position in the wood.
The web of the channel of the central leg 12 is said to keep the screw from moving out of aligned relationship with respect to the nested central leg and foot when the user has "slammed" the screw into the tree and has begun to rotate the nested central leg and foot to get the threads started into the tree. A difficulty with this structure, however, is best understood by examining FIGS. 5 and 7 of the Michael patent. As clearly seen in dotted lines in FIG. 7, the shank portion shown at 26 is spaced from the upper dotted lines delineating the channel web portion of the leg. The dotted lead line from the numeral 32 rests almost on the dotted line indicating the top of that web. The spaced-apart relationship of shank 26 from the channel web of the central leg 12 is also clearly seen in FIG. 5.
It has been found that the screw 16 will tend to flop back and fourth until the shank 26 contacts the end of the web either at the end of the shank or at the end of the "notch or space 32" which represents the end of the web.
The Michael structure also has a design problem in that the screw threads are tapered from beginning to end and because the diameter of the screw shank portion 26 is the same as the maximum diameter of the last of the screw thread. Because of this, after the screw is started into the tree, and the leg 12 is moved away from the screw to allow it to be put at right angles to the screw to help turn the screw, every turn of the screw requires far more force than the last. This will be understood from FIGS. 1 and 6 of Michael. More of the screw has to be forced at a greater and greater diameter as it is moved into the tree. Therefore, what may have been relatively easy at the beginning gets harder and harder as the screw is forced into the tree until at last, the cylindrical shank 26 is beginning to be drawn into the tree. Because this shank is of the same diameter as the largest diameter of the screw threads themselves, the forcing of this shank into screwed hole must enlarge the hole left by the screw threads up to the diameter of the shank. In order that the leg 12 is firmly situated against the tree as seen in FIG. 1, at least one or two revolutions of the screw after the shank 26 is in the hole will become necessary.
A further problem is that all of the torque on the screw to move it into and out of the tree must be transmitted through the pivot pin 24; and after a relatively small number of installations and removals of the tree step, the tendency of the pivot pin 24 to become bent or to fail is plainly evident.
Also, because the threads are tapered, if at any time and for any reason the screw starts to pull out of the wood, every outward movement will lessen the contact of the screw threads with the wood, and the failure will be sudden and extremely dangerous for anyone standing on or stepping on the step. This kind of failure can easily develop should the user apply more force than necessary on the last turn as the upper part of the leg 12 grinds and rotates into the bark of the tree. In order for the step to be positioned as seen in FIG. 1, the screw must be rotated until the leg 12 can hang vertically. In the case of the Michael tree step, because of the tapered screw, the step should always be forced in a counterclockwise direction as seen from the left in FIG. 1 and the screw always moved in tighter in order to arrive at a vertical positioning of the leg 12. This movement may cause the wooden "threads" formed by the screw to be "stripped." Any movement in reverse direction to align the leg to vertical position would back the tapered screw threads out of the wood so they will no longer have even the original full holding power to prevent a disastrous failure of the step.
As best seen in FIGS. 1, 3 and 4 of the Michael patent, all of the weight of a hunter or other user of the tree step on the step 14 is transmitted through a step pivot pin 20 and through leg 12 to the wood screw 16. Any deformation, bending or other failure of the pivot pin 20 will result in the sudden depositing of the person standing on the step 14 on the ground or to whatever lies beneath the step.
To overcome the initial crudities of my first portable tree step and to overcome the difficulties with the prior art, I have developed the present folding portable tree step.
Neither I nor those in privity with me are aware of any prior art structure more pertinent than those listed and discussed above. We know of no prior art which anticipates the claims herein.